Provide explicit function signatures for numba

[stestoll]

On my system, numba is crashing Python when @njit-decorated functions are called. The problem disappears when explicit function signatures are provided to @njit. Should we provides these?

[mtessmer]

Like Julia, numba can take advantage of multiple dispatch. This means I can njit function without specifying the type and it will work on several different types.

@njit
def myfunc(inp):
    return inp
   
print(myfunc(10))    # -> 10
print(myfunc('10'))  # -> '10' 

But once you specify a signature you can only use types of that signature.

@njit(''i8(i8)')
def myfunc(inp):
    return inp
   
print(myfunc(10))    # -> 10
print(myfunc('10'))  # -> TypeError: No matching definition for argument type(s) unicode_type

This is useful because it allows njit functions to be more dynamic. If I specify signatures, then I would need to specify all possible signatures if I want to maintain this functionality. In your specific case, using multiple signatures may not fix the crashing problem, so it may not even be worth it.

[mtessmer]

This issue appears to have been resolved with numba/numba#8852